The fluid power field basically remains an industry committed to a design philosophy wedded to the principle of packaging basic fluid operative valving elements in separate or distinct housings to form either a relatively simple or a complex dedicated control valve function. Generally speaking, these "valves", as commonly referred to in the industry, are then interconnected to one another to form a fluid power control circuit by means of conventional piping or manifold techniques.
This philosophy dictates that such a valve design can only be accomplished economically by the mass production of a given dedicated "valve" type in a special housing or package to reduce manufacturing cost to some feasible level. The attendant costs of this type of philosophy include maintaining a vast inventory of hundreds of different "valves" in hundreds of different dedicated valve bodies or packages. This remains true even though it has long been realized that all such valving functions are accomplished by a relatively few basic fluid operative elements, such as spools, poppets and the like.
More recently, a trend toward valve element cartridges has gained some attention in the field, however, again these are merely packaged in the similar great multiplicity of separate and distinct housings to form an elementary valving function which must be interconnected, often in a special body or housing, with other "valves" to form the desired control system.
In my prior U.S. Pat. No. 4,011,887, I disclosed a novel manifold design which could be employed in cooperation with the more or less conventional dedicated "valves" to perform the interconnection function between such dedicated "valves" in a compact and economical manner. Also disclosed in this patent was a valve package system which includes the basic fluid operative elements such as spools, mounted within the manifold body and interconnected to form a complete control system for a given application. While this form of power control system was a significant and valid improvement for some applications compared to the prior art, and the manifold principles disclosed therein represent a drammatic improvement over the prior interconnection means, the disclosed control system did not represent sufficient flexibility in design philosophy to provide a more complete and satisfactory solution to the most pressing present needs of the fluid power industry.
The fluid power industry, unlike the modern electronic science, has not been able to solve the huge cost of manufacture by reducing the operative functions to their most elementary state and create a package which is both economical and sufficiently flexible to perform a multitude of required control functions utilizing a relatively few basic standardized parts.
The present invention is directed to this problem and provides a control system which may be "programmed" or commanded in response to an interchangeable pilot control module arrangement to perform a wide variety of fluid power control functions in a very compact and economical manner.